A Phase III clinical trial including patients at the University of Oklahoma found that proton therapy improved survival and resulted in fewer side effects among people with head and neck cancer.
The trial was led by the University of Texas MD Anderson Cancer Center, enrolling 440 patients across 21 institutions.
It included oropharyngeal cancer patients, which includes the tonsils and the back part of the tongue. The incidence and mortality of oropharyngeal cancer have grown over the past three decades, particularly because of increases in HPV.
Researchers directly compared the impacts of proton and photon therapy on these patients.
Photon therapy is the most common type of radiation therapy, using high-energy X-rays to damage DNA inside cancer cells. Photons are wave particles: they don’t have physical mass, meaning they can pass in and out of the body.
But this also means radiation spreads beyond targeted areas, said Dr. Christina Henson, an associate professor of radiation oncology at the OU College of Medicine. In treating cancer in the neck, patients can experience side effects like dry mouth, sore throat and taste changes, making it difficult to eat. Some end up needing a feeding tube, she said.
Henson said photon therapy is a good treatment option. Now, she said, there’s an effort to help patients get through treatment with fewer side effects.
“There's constantly a search for ways to decrease the dose of radiation to the normal tissues that are surrounding the tumor,” Henson said. “And so proton therapy has been one avenue that's been explored for trying to do that.”
Protons have a physical mass and can be stopped at a certain depth inside tissue.
The therapy was first used in the 50s to treat limited areas in patients. Henson said its initial iterations weren’t precise. But, over the last decade, newer versions of proton machines have advanced to more effectively shape dosages.
In the trial, 221 patients were randomized to the proton group and 219 to the photon group. Five of them were patients at OU. Some patients in the proton section faced challenges with insurance declining to cover the therapy, Henson said, meaning they had to switch to the photon group.
Researchers found that, at five years, survival rates among patients who received proton therapy were 10% higher.
Henson said this seemed to be related to differences in the effects of radiation on the immune system.
“It seems that, potentially, the benefit of protons is that [they’re] just less toxic,” Henson said.
The trial’s findings may apply to other types of head and neck cancer, Henson said. She hopes the results will prompt insurers to cover proton therapy and additional trials on different cancers.
“Clinical trials often don't go the way we expect them to, right? We'll be really excited about a new therapy, and then the clinical trial shows that it didn't make any difference or sometimes even that it made things worse,” Henson said. “So when we do get a trial that's positive – especially when it's strongly positive like this – it is very, very exciting.”
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